Azeotropic distillation of 1-butanol from methyl nu-butyl ketone



March 14, 1950 A. sTElTz JR AzEo'rRoPIc DISTILLATIN oF Lam-mor. mou HETHYL n-BUTYL xEToNE Filed Nov. 18, 1948 Patented Mar. 14, 1,950

AZEOTROPIC DISTILLATVION OF l-BUTANOL FROM METHYL n-BUTYL KETONE Alfred Steitz, Jr.,

Tulsa, Okla., assignor to Stanolind Oil and Gas Company, Tulsa, Okla., a corporation oi' Delaware Application November 18, 1948, Serial No. 60,677 8 Claims. (Cl. 202-42) Thisinvention relates to the purication of alcohols. and more particularly to the separation of 1butanol from methyl n-butyl ketone.

My invention is a new method foi` separating l-butanol from mixtures thereof with methyl ,n-butyl ketone by fractionally distillin'g such mixtures in the presence of a hydrocarbon liquid means, such as extraction with water or other immiscible solvent, or by extractive distillation,

to separate a substantially pure l-vbutanol fraction.

having certain characteristics to be hereinafter deiined, and withdrawing a l-butanol overhead fraction substantially free from ketones and a residual methyl n-butyl ketone fraction substantially fre'e from 1butanol. Thereafter, I may separate a substantially pure l-butanol product from the overhead fraction by conventional means.

The major object of my invention is to separate l-butanol from methyl n-butyl ketone. Other objects are to prepare l-butanol and methyl nbutyl ketone in substantially pure form from a mixture thereof.

l-butanol and methyl n-butyl ketone cannot be separated by conventional fractional distillation, despite the substantial differences in their boiling points (117.7 and 127.2 C., respectively), owing to the fact that the two compounds form an azeotropic mixture boiling around 1l6.5 C. and containing 'approximately 18.2 percent by weight of methyl n-butyl ketone. The problem of eiecting this separation is of substantial commercial importance, owing to the fact that mixtures of 1butanol and methyl n-butyl ketonefare produced by various chemical processes, such as the so-called Fischer-Tropsch process, wherein carbon monoxide is hydrogenated over a suitable catalyst, the Synol process, which is a modified Fischer-'Iropsch process, operated at higher pressure and lower temperature, and various methods for the oxidation of normally liquid hydrocarbons.

I have now discovered that 1butanol can be separated from methyl n-butyl ketone in a convenient and advantageous manner by distilling a mixture thereof in the presence of a Cv hydrocarbon as an entrainer. Such hydrocarbons form minimum-boiling azeotropes with 1-butanol, but not with methyl n-butyl ketone. The boiling point of the 1-butanol is thereby depressed suiliciently below the azeotrope of l-butanol and methyl n-butyl ketone so that the 1,-butano1 may readily be distilled away from the methyl n-butyl ketone, leaving the ketone substantially free from 1-butanol. The resulting distillate fraction contains l-butanol and entrainer liquid, free from methyl n -butyl ketone, andI may subseplete suppression of the distillatel substantially more diirlcult.

The' primary distillation of the azeotrope of 1j butanol and entrainer liquid is preferably carried out in the substantial absence of water, since in the presence of water, vbinary and ternary azeotropes tend tobe formed, rendering the commethyl nbutyl ketone from Suitable entrainer liquids for use in my process must form a binary azeotropic mixture with 1- butanol boiling sufficiently below the boiling point (116.5" C.) of the azeotrope of l-butanol and methyl n-butyl ketone to be separated therefrom by conventional fractional distillation. Moreover, the entrainer liquid preferably should not form an azeotropic mixture with methyl n-butyl ketone; or if it does form such an azeotropic mixture,` the boiling point thereof should be far enough below the boiling point of the azeotrope of l-butanol and methyl n-butyl ketone to permit the separation of the azeotropes by fractional distillation. For this purpose, Cv hydrocarbons in general are satisfactory, including aliphatic hydrocarbons such as l-heptene, nheptane, and the like; cycloaliphatic hydrocarbons such asdimethylcyclopentane, methylquently be further processed by conventional cyclohexane, 4-methylcyclohexene, and the like; and toluene.

The attached owsheet illustrates an advantageous embodiment of my invention. For simplicity, various items of equipment such as valves,

' pumps, heat exchangers, and the like, have been omitted from the drawing.

A mixture of l-butanol and methyl n-butyl ketone isintroduced through line |0| into an intermediate section of fractionator |02, equipped with reboiler |03. Therein, the mixture is fractionally distilled in the presence of a suitable entrainer liquid, such as toluene, which is introduced into the column through line |04, and an azeotropic mixture of 1butano1 and toluene is withdrawn overhead through condenser |05. From the bottom of fractionator |02 a stream of methyl n-butyl ketone substantially free from l-butanol emerges through line desired, by fractional distillation or by other conventional means.

The overhead stream from fractionator |02 is rei'luxed in part through line |01 to the top of the column, and the remainder is withdrawn through line |08 and introduced into the hntfnm I06,'and is Withdrawn. This stream may be further puriecl, if

tractor through line action of reboiler of extractor column |09. Within the extractor, the mixture of toluene and l-butanol ilows upward countercurrent to a descending stream of water, which is introduced into the top of the ex- ||0. The water extracts all or the major proportion of the 1,-butanol from the toluene. The washed toluene flows out of the top of the extactor through line IH, and is recycled through line |04 to fractionator |02. Makeup toluene liquid is added to line |04 through line i |2 as required.

An aqueous solution of l-butanol, contaminated with a minor proportion of toluene, flows out of the bottom of extractor |09 through line H3, and is introduced into an intermediate section of stripper column H4, equipped with reboller H5. The l-butanol and toluene are stripped out of the. aqueous stream by the action of the reboiler and/ or free steam, introduced if desired into a lower section oi the stripper column through line H6; and a mixture of l-butanol, toluene, and water is taken oi overhead through condenser H1. A lean aqueous stream ows out of the bottom of stripper H4 through line H8, and is recycled in part to the top of extractor |09 through lines H9 and H0. Excess water is withdrawn through line |20 and discarded; and makeup water is added to line H0 as required through line |a.

The liquid from condenser H1 is refiuxed in part to the top of stripper column H4 through line |'2 I, and the remainder is withdrawn through line |22 to decanter |23, where stratification takes place. The aqueous phase therefrom, containing a small proportion of dissolved l-butanol and toluene, is returned to stripper column H4 through line |24, preferably at an intermediate section. The organic phase, comprising predominantly l-butanol, plus a small proportion of dissolved water and toluene, is led through line |25 into an intermediate section of drier column IZE. Within drier column |26 substantially all of the water and toluene, together with a quantity of l-butanol, is distilled overhead by the |21 through condenser |28, and a purified, substantially anhydrous l-butanol stream emerges from the bottom of the column through line |29.

The liquid from condenser |28 is reuxed in part to the top of drier column |26 through line |30, and the remainder is withdrawn through line |3| to decanter |32. The aqueous phase from the decanter contains a small proportion of dissolved l-butanol and toluene, and is suitably recycled through lines |33 and |24 to stripper column H4. The organic phase, comprising predominantly 1-butanol and toluene, is suitably recycled through lines |34 and |08 to the bottom of extractor column |09.

My invention will be more fully understood from the following specific example.

Into a batch still were introduced 113.5 parts by weight of a mixture of l-butanol and methyl n-butyl ketone containing 10.8 percent by weight of the ketone, and 410.4 parts by weight of nheptane, and the total mixture was fractionally distilled through a packed column. After 4'76 parts by weight of distillate had been withdrawn,

4 the distillation was stopped, and the distillate fraction and the residue were analyzed.

The distillate fraction was found to contain 85.5 parts by weight of l-butanol, with no detectable quantity of methyl n-butyl ketone.

The residue contained 11.8 parts by weight of methyl n-butyl ketone.

While the above example and flowsheet illustrate advantageous embodiments of my invention, it is to be understood that I am not limited thereto. My invention is to be construed broadly within the scope of the description and the claims, and in general it is to be understood that any modifications or equivalents that would ordinarily occur to those skilled in the art are to be considered as lying within the scope of my invention.

In accordance with the foregoing description, I claim as my invention:

1. In a process for separating l-butanol from methyl n-butyl ketone, the steps which comprise fractionally distilling a mixture thereof in the presence of a C'z hydrocarbon and separating an overhead fraction comprising 1butanol substantially free from methyl n-butyl ketone.

2. The process of claim 1 wherein said hydrocarbon liquid comprises predominantly an aliphatic hydrocarbon.

3. The process of claim 2 wherein said hydroctzarbon liquid comprises predominantly n-hepane.

4. The process of claim 1 wherein said hydrocarbon liquid comprises predominantly a cycloaliphatic hydrocarbon.

5. The process of claim 4 wherein said hydrocarbon liquid comprises predominantly methylcyclohexane.

6. The process of claim 1 wherein said hydrocarbon liquid comprises predominantly toluene.

'7. In a process for separating 1butanol from methyl n-butyl ketone, the steps which comprise fractionally distilling a mixture thereof in the presence of a C1 hydrocarbon and substantially in the absence of water, and separating an overhead fraction comprising l-butanol substantially free from methyl n-butyl ketone.

8. In a process for separating 1butanol from methyl n-butyl ketone, the steps which comprise ractionally distilling a mixture thereof in the presence of a C1 hydrocarbon, and separating a rst fraction comprising l-butanol substantially free from methyl n-butyl ketone and a second fraction comprising methyl n-butyl ketone substantially free from l-butanol.

ALFRED STEITZ, JR.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,085,546 Roelfsema June 29, 1937 2,324,255 Britton et al July 13, 1943 2,351,527 Lembecke June 13, 1944 OTHER REFERENCES Analytical Chemistry, vol. 19, pages 550 and 566 (August 1947). 

1. IN A PROCESS FOR SEPARATING 1-BUTANOL FROM METHYL N-BUTYL KETONE, THE STEPS WHICH COMPRISE FRACTIONALLY DISTILLING A MIXTURE THEREOF IN THE PRESENCE OF A C7 HYDROCARBON AND SEPARATING AN OVERHEAD FRACTION COMPRISING 1-BUTANOL SUBSTANTIALLY FREE FROM METHYL N-BUTYL KETONE. 